Among-strain consistency in the pace and shape of senescence in duckweed

1.Comparative studies have demonstrated extensive variation in age-trajectories of mortality and fecundity, both within and among species, with many taxa exhibiting a general pattern of age-related demographic decline referred to as senescence. Whereas a considerable body of theory is devoted to explaining the origin and persistence of senescence, the evolutionary forces underlying variation in demographic trajectories more generally remain poorly understood. 2.Studying variation in demographic trajectories is complicated by the fact that different species (or even different populations of a given species) may live and reproduce on different time scales, which, for comparative purposes, can make it challenging to disentangle patterns of age-related demographic change (the shape of demographic age trajectories) from the time scale on which those changes happen (the pace of demographic age trajectories). 3.Here we examine variation in the pace and shape of demographic trajectories a...1. 比较研究已证实，不同物种内部及物种间的死亡率（mortality）与繁殖力（fecundity）的年龄轨迹（age-trajectories）存在广泛差异。诸多分类群（taxa）呈现出与年龄相关的种群衰退（demographic decline）的普遍模式，即衰老（senescence）。尽管已有大量理论致力于阐释衰老的起源与维持机制，但总体而言，驱动种群轨迹（demographic trajectories）变异的进化力量仍未得到充分解析。 2. 研究种群轨迹的变异存在一项复杂挑战：不同物种（乃至同一物种的不同种群）的生存与繁殖时间尺度各不相同。从比较研究的视角来看，这使得我们难以将与年龄相关的种群变化模式（即种群年龄轨迹的形态（shape））与这类变化发生的时间尺度（即种群年龄轨迹的速率（pace））区分开来。 3. 本研究旨在考察种群年龄轨迹的速率与形态的变异……